Watercraft hydrofoil device



June 16, 1959 H. BOERICKE, JR

WATERCRAFT HYDROFOIL DEVICE 4 Sheets-Sheet 2 Filed May 1, 1957 ZERO SPEED WATERLINE I 7%56 56 &

ZERO SPEED WATERLINE June 16, 1959 BOERCKE, JR 2,890,672

WATERCRAFT HYDROFOIL DEVICE Filed May 1, 1957 4 Sheets-Sheet 3 ZERO SPEED WATERLINE TOP SPEED WATERLINE ZERO SPEED WATERLJNE TOP SPEED WATERLINE 1N VENT OR HAFO 1.0 BQERICKEIJR.

, BY ZLZLL ATTORNEY n 16, 1959 H. gOERICKE. JR 2, 90 61 WATERCRAFT HYDROFQIL DEVICE Filed May 1, 1957 v 4 Sheets-Sheet 4 v TIE-[5. DESTRUCTIVE Q DESTRUCTIVE q CAVITATION g NO CAVITATION p I CAVITATION 45 KNOTS 55 KNOTS s5 KNOTS 9 NO CAVITATION NO CAVITATION Q E 4/////7/i/'/71ii1;,,,...

45 KNOTS 55 KNOTS 65 KNOTS' I N-DESTR TIVE vmmom Fl NO CAVITATION NO CAVITATION VAgQ c Q g Jam 45 KNOTS 55 KNOTS 65 KNOTS r DESTRUCTIVE NO CAVITATION 'g i fifixfigx Q T'QN 45 KNOTS 55 KNOTS 65 KNOTS 5 DESTRUCTIVE 1////// ////1 lllllllllllll 45 KNOTS 55 KNOTS a5 KNOTS kDN-DESTRUCTNE C NO CAVITATION c: NO CAVITATION g AVT will/[Ill llW/I/l/I/l/l/A lII/l/l/l/I/I/l/I/A 45 KNOTS 55 mars s5 KN0T HAROLD BOERICKEJR BY 8- L. TTORNEY sigued for;top speeds less than about 5. O; knots.

i whiclr alloyv slightlyyhigherspeeds free of ariab gent-1e curves approaching those oi acircle"; theseh di'ofoils and strut' sections vvill 'b'e' r'le iiefred' fohefe tjeras "ease. or he ray-disten- United States Patent WATERCRAFT'HYBRBFOILBEVIGE I 1 Harold Boericke,- .fn wasliington, 15.6. Application May 1', 1 957, swarms. 656,469

11 Claims: c1; 114 -665)- (Granted under Title as -us. cbue (1952);see; 2'66) The inventiondesci'i-h'ed herein may be manufactured and used by' or for the Government of the" United States of America for governmental purposes without th'epaym'e'ntof any royalties ther'eon or therefor.-

This invention relates tohydr ofoil' craft and more particularly to cavitatiomadapted hydrofoils for supporting 20 such craft in flight.

Briefly; the formation of cavitation an embody proseeding through: water isrelated to the shape of the body, the speed: of the body and its depth below the surface of the water. In particulaigit is governed by th'minimuminegative pressureexpenence'd onthe' body. lfthis pressure dropsbelowthe vapof pressure of' Wetter; abou "3?'pissi.,.arbubble'of water vaporis formedz The purpose of applicants novel cavitation-adaptedhydifofo'illisiti allow a hydrofoil 'b'oat'- to operatc at 4 a high 'siipercavitatingitop speed and -still take ofi at a low speed.

' Ahydrofoil boat makes=thefdllestuse of: its capa bilities orilyfifiit is foil-borne throughas muchofithespEed range as: possible. Until recently," top speed has' 'beein limited thez'onset of variable cavitation on thefoil'pand talreotfi'speedkhas-wbeeri leept high the limitedhydrofoil lifting. area available; Requirements :for alarge foilborne speed range .present a severe:cmi romise'to'thedesigner. x i '1 Hydrofoil -.botits now opera-tingthave foils proportioned f om. data furnished-for airplane-Wing seetions operating at subsonie: spfeeds: Such-hydrofoil an'd st-rut sections,

hereinafter calledtypfem and o respeetivelmare'ofaconv,zventioiia'l teardrop shape -and proveito be efficienbat I xspe'edseup to abQut SO-lmms. Aegreaten speeds; the 'suction on the top face of ltl'iese -hydroiioilsg'Wlrieh forms a 4 large part: on tlre li ies becomes: so" gTGHEBS- to cause suction; As -tl1e water-.flovv? cairifesdhcmpastthe region where theyiiare formedptl'ie pressure decreases again,

and the 'bnbbles collapse. ThGeShOtZk oi collapse isflcon cenltrat ed at a tir i'y point This PBiKEiS'PgEHETaHYi(Hi the surface- 1 of the hydrofoilso that aparticle: 0ft the, metal is eroded away, a process; which,.ii Contifluedwantsoon destroy theiefl i'ei'ency' of. the foil: Thevformation. and 1 collapse-inf :wzitervapor bubblesf is walled variable cavita tion-and becztifiise of it, -present--hydrofo ilz boats are detFurthe -investigations have developed'h drofoil shapes itation. The cross sections are-characte'r izedib hydrofoil? snow a night y argues topspeed fee: the

fiecerit' investigations havedeveloped' hydrofoii and sue-e shapes which ean iopeeate ebntinuouslysao eavitatar ing speeds without damage to the metal. Characterized I p of shape 0; theflsupercavitating shape. a cessive change in type of: sectional shapes, the hydrofoil Q i's adapted-"to the cavitation conditions which it'willjm'eet at: the various operatingwaterlines;

- attenuation 2,890,672 Patented June 16, 1959 ."ice

- i 2 by a fixed Water vapor bubble which extends for the length of the hydrofoil and trails beyond it, this t ype of operation isknown as supercavitating-fiow. Sections designed for it,- are generally of a wedge shape the 5 sharpedge forward and a bluntedge aft. These foiland strut sections will hereafter be referred to as sections 0 and 0; respectively. Since the top surface of the foil contacts only water vapor, and the bottom surface: is the only one which is yvettedlthe drlag is low, arid the em- 10 ciency can be excellent. Foils designed for suchconditi'ons are notlimited by any top speed presently known,

and thus greatly extend the speed capabilities of hydro- 'foiiboats. H A p Low take off speed in hydrofoil boats can be achieved either by disposing small foil surfaces at a large angle of emerging the foil surfaces until; at high'speedthey ride only on the lowestsurfaces; This is; because fora given angle of attack and l-ifi jorce thehydrofoilneeds less area at; higher speeds. Foils ofthe ladder,- surface piercing and diamond;shapealso provide a-reserveaofarea to preuvent lo'ssiof flight, oftencalled' crashing. Ifjor any reason thehydrofoilsshould lose lift through fo lingior waveaetiom-a'dropping of thehulloccurs; Igniboats usi -n'g hydrofoils at the above type reserve lifting areas heeome itnrnersed-a-nd give additional lift, thli spreventingeenougli dropping to cause thehull to; strike the'water. Inso farasapplicant; has-beenfable to determine, present hydrofoils are not designed for supercavitating' speeds, -andwill not operate efiiciently at speeds greater than iv aliqubSO-knots.

. '1 From the high-and speed considerations;applicant deducedthat-it isdesirable to-incorporate in agiven hydrofoil' amadaptationto cavitation, so that-at low speed .vyhemth 'upper surfaces are immersed, these upper sur- :faces are formed of shape a; an efficient shape for suboavita-ting speeds. For intermediate speeds when intermediate surfaces are] immersed, these intermediate surfaces are formed-ofishape'bg Thenwhen athigh; speed, only the lowest surfacesareimmersed-the se sections are Thus; by a" suc- V Strutsections a, b',-:and;- are similarly fashioned for low,-- intermediate 1 andjtop speeds, respectively,- I 5e Accordingly; a broad objectof the present-invention 1 is; to==1irovide an improved hydrofoil.-

A further" object of this' invention is to provide a: hy-

i .drofoii that operates efficiently atvarious" speeds.-

rnore'specific objectof thisinvention isdopifovide adapted hydrofoil designed to allovv abysmoperate-at high supercavit'atiiig top speed "and'fstill were 01f emeiessy at low speed H 1 Other-objects andnianyo f the attendantdama es ruin invention 'will b'e' readily appreciated "'tliesaine ing' de'taiiled description whenconsi'dered in connection with the accompanying drawings in 'vvliiclflike'fr'fr ence characters designate" like parts" thiengfioumuaseverai fviews' thereof'andvvhereing i A Fig-q 15 front elevational view illustratii g-v one type of hydrofoil incorporating tli present invention;

Fig. 2 is a side elevational view of the hydrofoil shown in Fig. 1;

Figs. 3, 4 and are transverse sectional views taken on lines 33, 4-4 and 55 respectively, of Fig. 1, and illustrating foil sections in accordance with this invention;

Figs. 6, 7 and 8 are transverse sectional views taken on lines 66, 77 and 8--8, respectively, of Fig. 9, and illustrating strut sections in accordance with this invention;

Fig. 9 is a front elevational view illustrating a second type of hydrofoil incorporating this invention;

Fig. 10 is a side elevational view of the hydrofoil shown in Fig. 9;

Fig. 11 is a front elevational view illustrating a third type of hydrofoil incorporating this invention;

Fig. 12 is a side elevational view of the hydrofoil shown in Fig. 11;

Fig. 13 is a front elevational view of a fourth type of hydrofoil incorporating this invention;

Fig. 14 is a side elevational view of the hydrofoil shown in Fig. 13;

Fig. 15 is a perspective view of the hydrofoil shown in Figs. 13 and 14;

Fig. 16 is a schematic view showing cavitation formation on the various hydrofoil sections at different speeds; and

Fig. 17 is a similar schematic view showing cavitation formation on the various strut sections at different speeds.

Referring now to the drawings, first to Figs. 1 and 2, wherein for purpose of illustration there is shown in broken lines a starboard side portion of a hull 20 upon which is mounted a bracket mechanism 22 which in turn mounts a cavitation-adapted, modified diamondshaped hydrofoil 24. A similar hydrofoil, not shown,

may be mounted on the port side of the hull. The mounting of the hydrofoil is generally similar to that disclosed in applicants copending patent application Serial No. 555,213, filed December 23, 1955. Therefore, for a complete description of the mounting mechanism, reference may be had to such copending application.

Hydrofoil 24 comprises an upper or inverted V portion including a pair of inclined foil-members 28, a

4 inclined members 30 and the base member 32 of lifting surfaces of the b type (Fig. 4), and forming the strut 38 with a surface of type a (Fig. 6).

Referring now to Figs. 3 to 8, inclusive, which illustrate typical hydrofoil and strut shapes in accordance with this invention, wherein:

Shape a (Fig. 3) is a hydrofoil section having the shape of a teardrop characterized by a rounded lead ing edge, a sharp trailing edge, a center of volume ahead of its midpoint, a convex upper surface, and a convex or convex-concave lower surface;

Shape b (Fig. 4) is a relatively flat hydrofoil section characterized by a sharp or slightly rounded leading edge, a sharp trailing edge, a convex top surface approximating an arc of a circle, and a straight or concave bottom surface, also approximating an arc of a circle;

Shape c (Fig. 5) is a hydrofoil section having a wedge shape characterized by a sharp leading edge, a blunt trailing edge, a convex, or convex-concave top surface, and a concave bottom surface approximating the arc of a circle;

Shape a (Fig. 6) is a symmetrical strut section char- -acterized by a rounded leading edge, a sharp trailing edge, a center of volume ahead of its midpoint, and both surfaces convex, or convex-concave;

. Shape b (Fig. 7) is a symmetrical strut section characterized by a sharp or slightly rounded leading edge, a sharp trailing edge, and both surfaces convex, approximating an arc of a circle; and

'Shape c (Fig. 8) is a symmetrical strut section characterized by a rounded leading edge, a blunt trailing edge, and both surfaces convex, approximating a cubic parabola.

' Strut 44 may be attached to the watercraft by any suitable means not shown.

lower U-shaped portion including a pair of inclined foil members 30 and a base foil 32, and an intermediate horizontal brace and foil member 34; all of which foil members are welded into a unitary structure substantially within a single plane as shown in Fig. 2. At the top of the inverted V, the hydrofoil is connected by a strut 36 to the bracket mechanism 22 and at the inis with the hydrofoil 24 (Figs. 1 and 2) the upper inclined members 28 and the horizontal spanner 34 are each made up of lifting surfaces of the a type (Fig. 3); the lower inclined members 30 are made up of lifting surfaces of type b (Fig. 4); the base member 32 is made up. of a lifting surface of the c type (Fig. 5); and the strut 38 is made up of a surface of the a type (Fig. 6).

The lifting surfaces of the diamond-shaped hydrofoil 24 (Figs. 1 and 2) may be modified within the scope of this invention. That is, one modification consists of forming the upper inclined lifting members 28, the horizontal spanner 34 and the lower inclined members 30 of lifting surfaces of the a (Fig. 3) type, with the base member 32 formed with a lifting surface of the c type (Fig. 5), and with strut 38 formed with a surface of the a type (Fig. 6).

Another modification of the diamond-shaped hydrofoil (Figs. 1 and 2) consists of forming the upper inclined members 28 and the horizontal spanner 34 with lifting surfaces of the a type (Fig. 3), forming the lower In this embodiment (Figs. 9 and 10) of the invention, the upper foils 41 are formed with lifting surfaces of the a type (Fig. 3), with strut section 44 of the a type (Fig. 6); the intermediate foils 42 are formed with lifting surfaces of the b type (Fig. 4), with strut section 45 1 of the b type (Fig. 7); and with base foil 43 formed with a lifting surface of the 0 type (Fig. 5), with strut section 46 of the 0' type (Fig. 8).

A first modification of the cavitation-adapted, laddertype hydrofoil 40 (Figs. 9 and 10) comprises forming the upper foils 41 and the intermediate foils 42 of the a type (Fig. 3) lifting surfaces, with strut sections 44 and 45 of the a type section (Fig. 6); and with the bottom foil 43 formed with the c type (Fig. 5) lifting surface, with strut section 46 formed of either the b type (Fig. 7) or the 0 type (Fig. 8).

A second modification of the cavitation-adapted, laddertype hydrofoil (Figs. 9 and 10) comprises forming the upper foils 41 and intermediate foils 42 of the a type (Fig. 3) lifting surface, with strut sections 44 and 45 of the'a' type (Fig. 6); and with the bottom foil 43 formed of the b type (Fig. 4) lifting surface, with strut section 46 formed of the b type (Fig. 7).

Figs. 11 and 12 illustrate a second cavitation-adapted,

, ladder-type hydrofoil incorporating the present invention. Here the hydrofoil 50 comprises an upper pair of inclined foils 51 connected by a horizontal foil 52, an

; intermediate pair of inclined foils 53 connected by a horizontal foil 54, a horizontal base or bottom foil 55,

an upper pair of strut sections 56, an intermediate pair of strut sections 57 and a lower pair of strut sections 58;

all welded into a rigid unitary structure. Strut sections 6 may be-use'cFto' attach then-ydrofoil to tirewarererah by' suitable means nor-shown). I I

In this (Figs. ll'and 12)f embodimentofthe invention, the upper inclined'foils 51' andtlie. horizontal foil 52 are formedwith nflingsurfaces of'the atype (Fig. 3') with upper strut sections 56"of'the', mtype (Fig.v 6);.With the intermediate of incliried'foils' 53 andhorizontal foil'54 formed of the b type (Fig. 4) and intermediate strut sections 57 of the b type (Fig. 7); and with the base or bottom foil'ssformedj of the c type (Fig. 5) andbottom strut sections-of the c" type (Fig. 8).

The type of ran and' strut sections may be modified in the embodiment of. the invention illustrated'in Fig's. 11 and 12in substantially the. same manner as that described above with reference to the embodiment illustrated'in Figs. 9 and; 10, dependinguponthe types of craft withwvhich the hydrofoillis to. beusedl Figs. 13-15 illustrate a third'cavitation-adapted, laddertype hydrofoil incorporating the present invention. With.

'sections ti t and-a-pair of'lowerstrut 'sections 65". Except for the-bottom-foil- 63,- whichd's pivotally mounted on.

the bottoms ofstrut-section s: 65,- the foil and: s'trutsec- }fions 5 are weldedinto arigid unitary: structu re with the 'strutseot-ions-insubstantiallyp'ara'lle'l vertical planes-and,

as shown in Fig. 14, with the entire hydrofoil assembly in one major vertical plane. Strut sections 64 may be used for attaching the hydrofoil to the watercraft by suitable means (not shown).

In this (Figs. 13-15) embodiment of the invention, the pair of loop-shaped foils 61 are formed with lifting surfaces of the a type (Fig. 3) with the upper strut sections 64 of the a type (Fig. 6); with horizontal foil 62 formed with lifting surfaces of the b type (Fig. 4); and with bottom foil 63 formed with the type (Fig. lifting surfaces, with the lower strut sections 65 formed of the 0' type (Fig. 8) section. As with the other embodiments of the invention, the foil and strut sections in this (Figs. 13-15) embodiment may be modified to fit speed and load conditions.

This operation of the various hydrofoil sections, that is, the regimes of flow with their attendant speeds is graphically illustrated in Fig. 16. As shown, up to speeds of about 45 knots there is no cavitation on hydrofoil sections a, b or c, and at this speed, with applicants invention, all three sections maybe beneath the surface of the water. At speeds of about 55 knots there would be destructive cavitation on section a and no noticeable cavitation on sections b or c. However, in accordance with the instant invention, only sections b and c are immersed at 55 knots, so that section a is not effected by this speed. At 65 knots there would be destructive cavitation on sections a and b and nondestructive cavitation on section c. However, again in accordance with the instant invention, only section c is immersed at 65 knots, so that sections a and b are not affected by this high speed. As shown, at 65 knots a fixed water vapor bubble or nondestructive cavity is formed on section 0 from the leading edge, across the top surface to a point well beyond the trailing edge.

Fig. 17 graphically illustrates the operation of strut sections a, b and c at the various speeds that they may be submerged in the same manner as that described immediately above for the hydrofoil sections.

Thus, it is shown, in accordance with this invention, the various hydrofoil sections and the various strut sections are so shaped and so chosen relative to each other and to the various speeds of the craft as to be free of destructive cavitation thereon at any speed during which such surfaces are normally submerged.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that numerous modifications or alterations may be made therein without departm from the spiiit and the sco e of the invention as set-remit the appended claims.

What is olaimed'is: I

1. A cavitation-adapted hydrofoil arran ed below the hut-1 or. a-wa'tercraft' and eem fising' ,a.p1-ura1ity or verticalm-spaced liftiiigsurfaces constructed and ffafig e'd in a manner that as the speed; of'the cranincreases' the craft rises progressively ou er the ater successively emerging the foil lifting; rfac'e's' uiitil" at top speeaj the craft rides only. the lowerzlifting surfaee's,,said lifting surfaces having cross-sectioiial shapes. suehi as.- to be'fi'e'e of destructive cavitation. thereon at; aii'y during which suchsurfacesareqiiormally submer ed, s ia vertically-spaced liftingsurfaces'include J liftiiigl su'rface havinga crossrsect'ional' shape simulatiiiga teardrop, an. intermediate surface having. a relatively thin crossrsectionaln shape. comprising. gentle and. a lower. lifting surfacehavinga cross-sectidnahsliape simulatinga. wedge. I I I 21. A.cavitation.-adapt ed'.hydrofoil.as set forth iiiclaiin 1. wherein. the vertically-spaced surfaces are. connect'ed. bystrut. members having cross s'ectiona-L shapes such. as be. freev of destructive cavitation.-thereon. at any speed. during; which the.- stiilt members. are. normally submerged, said strut members includenupper strut having, at symmetrical.;crosseseotional. shape. simulating a teardrop, an intermediate strut having asymmetrical cross-sectional shape comprising two convex surfaces each approximating an arc of a circle and a lower strut having a symmetrical cross-sectional shape comprising two convex surfaces each approximating a cubic parabola.

3. A cavitation-adapted hydrofoil as set forth in claim 1 wherein the hydrofoil is connected to the watercraft by a strut having a cross-sectional shape simulating a teardrop.

4. A cavitation-adapted hydrofoil as set forth in claim 1 wherein the plurality of vertically-spaced lifting surfaces include an upper inverted V-shaped member, an intermediate substantially horizontal member and a lower substantially U-shaped member, all of said members being united into a unitary structure.

5. A cavitation-adapted hydrofoil as set forth in claim 4 wherein the upper inverted V-shaped member and the intermediate horizontal member comprise a cross-sectional shape characterized by a rounded leading edge, a sharp trailing edge, a center of volume ahead of its midpoint, a convex top surface, and a convex lower surface, wherein the lower U-shaped member includes a pair of inclined legs connected by a horizontal bottom member with the inclined legs comprising a cross-sectional shape characterized by a relatively shanp leading edge, a sharp trailing edge, a concave top surface approximating an arc of a circle and concave bottom surface approximating an arc of a circle, and wherein the bottom horizontal member comprising a cross-sectional shape characterized by a sharp leading edge, a blunt trailing edge, a convex top surface and a concave bottom surface approximating an arc of a circle.

6. A cavitation-adapted hydrofoil as set forth in claim 1 wherein the plurality of vertically-spaced lifting surfaces include an upper pair of diverging members, an intermediate pair of diverging members and a lower horizontal member, connected by struts into a unitary structure.

7. A cavitation-adapted hydrofoil as set forth in claim 6 wherein the upper pair of diverging members comprise a cross-sectional shape characterized by a rounded leading edge, a sharp trailing edge, a center of volume ahead of its midpoint, a convex top surface, and a convex lower surface, wherein the intermediate pair of diverging members compnise a cross-sectional shape characterized by a relatively sharp leading edge, a sharp trailing edge, a concave top surface approximating an arc of a circle and concave bottom surface approximating an arc of a circle and wherein the lower horizontal :member comprises a cross-sectional shape characterized by a sharp leading edge, a blunt trailing edge, a convex top surface and a concave bottom surface approximating an arc of a circle.

8. A cavitation-adapted hydrofoil as set forth in claim 1 wherein the plurality of vertically-spaced lifting surfaces include an upper section comprising a pair of inclined members connected by a horizontal member, an intermediate section comprising a pair of inclined members connected by a. horizontal member, and a lower section comprising a horizontal member, all connected into a unitary structure.

9. A cavitation-adapted hydrofoil as set forth in claim 8 wherein the upper section comprises a cross-sectional shape characterized by a rounded leading edge, a sharp trailing edge, a center of volume ahead of its mid-point,

' a convex top surface, and a convex lower surface, wherein the intermediate section comprises a cross-sectional shape characterized by a relatively sharp leading edge,

a sharp trailing edge, a concave top surface approximating an arc of a circle and concave bottom surface aprproximating an arc of a circle, and wherein the lower section comprises a cross-sectional shape characterized by a sharp leading edge, a blunt trailing edge, a convex top surface and a concave bottom surface approximating an arc of a circle.

10. A cavitation-adapted hydrofoil as set fonth in 10 wherein the upper section comprises a cross-sectional shape characterized by a rounded leading edge, a sharp trailing edge, a center of volume ahead of its mid-point, a convex top surface, and a convex lower surface, wherein the intermediate section comprises a cross-sectional shape characterized by a relatively sharp leading edge, a sharp' trailing edge, a concave top surface approximating an arc of a circle and concave bottom surface approximating an arc of a circle and wherein the lower section comprises a cross-sectional shape characterized by a sharp leading edge, a blunt trailing edge, a convex top surface and a concave bottom surface approximating an arc of a circle.

References Cited in the file of this patent FOREIGN PATENTS 517,519 Germany Feb. 4, 1931 572,413 Great Britain Oct. 8, 1945 715,850 Great Britain Sept. 22, 1954 760,525 Great Britain Oct. 31, 1956 820,896 France Aug. 9, 1937 

